The Splendid Magic
of Penny Arcade:
11 1/2 Anniversary Edition
This book details the history of a comic strip called Penny Arcade. The comic appears to catalog the lives of two young men who are utterly steeped in popular culture.
Each chapter gathers into a coherent beam of savory trivia, strange facts, formerly mysterious origins, biographical information, interviews, inaugural conventions, an unlikely charity, and comic strips.
You get the sense that some of the content may be apocryphalfor example, the part where they eat a whole wolf basically comes out of nowhere.
Also, if one of them really did become King of the Britons, you're sure you would have heard about it somewhere else.